Do these use the factory mounting points or do I need to modify anything?

These mount at the factory tail light points — no drilling or modification required. They're a direct bolt-in replacement for the OEM housings.

Are the LED bulbs included or do I need to source them separately?

The housings come as assemblies only. You'll need to transfer your existing bulbs from the OEM lights or source compatible LED bulbs for the socket type.

Will these work with my truck's electrical harness right out of the box?

These use standard tail light connectors. Plug them into your existing wiring harness — no custom wiring or splicing needed.